US Bridges

Mountain Avenue over I-78

Fair

Somerset County, New Jersey · 0.46 MI E of I-78 Exit 36 · Structure no. 1817170

Built
1965
60 years old, rebuilt 1995
Condition
Fair
inspected July 2024
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
255 ft
4 main spans
Daily traffic
4,780
2022 count
Owner
State
State Highway Agency

About this bridge

Mountain Avenue over I-78 is a prestressed concrete stringer/multi-beam or girder carrying Mountain Avenue over I-78 in Somerset County, New Jersey. It was built in 1965 and reconstructed in 1995, so it is 60 years old, older than the New Jersey average of 58.5 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 6 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

It carries about 4,780 vehicles a day, roughly 3% of them trucks, projected to reach 5,830 by 2042. The structure is 255 ft (77.7 m) long and 44 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

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CarriesMountain Avenue
CrossesI-78
Location0.46 MI E of I-78 Exit 36
RouteCity Street 0
CountySomerset County
StateNew Jersey
Coordinates40.64744, -74.51344
Functional classUrban Collector

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJuly 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Approach roadway alignment6: Equal to present minimum criteria
Operating rating92 US tons
Inventory rating38 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20 + Mod
Structure length255 ft (77.7 m)
Longest span90 ft (27.4 m)
Deck width44 ft (13.4 m)
Roadway width29 ft (8.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic4,780 (2022)
Projected traffic5,830 by 2042
Trucks3%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesHighway
Detour if closed3.1 mi (5 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedOther structural work, including hydraulic replacements
Estimated improvement cost$4,000 (2022 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was Mountain Avenue over I-78 built?

It was built in 1965, making it 60 years old in 2025. It was reconstructed in 1995.

What condition is Mountain Avenue over I-78 in?

The National Bridge Inventory rates it in fair condition. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. The last reported inspection was in July 2024.

How much traffic does Mountain Avenue over I-78 carry?

About 4,780 vehicles per day (2022 count), of which roughly 3% are trucks.

How long is Mountain Avenue over I-78?

The structure is 255 ft (77.7 m) long with a longest span of 90 ft (27.4 m) and a deck 44 ft wide.

Who owns Mountain Avenue over I-78?

It is owned by the State Highway Agency.